"EMC shares were up 4.88% to $21.29 in early trading, closing in on its 52-week high of $21.83," the Wall Street Journalreported Thursday.

But EMC's stock dropped back to $21.21 by the end of the day Thursday, and had dropped again to $20.97 by 10:30 a.m.EST eastern time Friday morning.

Oracle shares, meanwhile, dropped from $28.66 to $28.33 on Thursday, and dropped slightly more Friday morning.

The Oracle/EMC rumor seems to have been fueled by a research note from Citigroup analyst Walter Pritchard, who listed potential buyout targets for Oracle. Even Pritchard seemed to think a deal unlikely, describing Oracle/EMC as a "potential long shot," according to Barron's Tech Trader Daily. Pritchard said BMC Software, Cerner and Mellanox are more likely targets for Oracle.

Oracle is among the most acquisitive companies in the tech industry, but integrating EMC into its vast portfolio could be challenging as Larry Ellison's software giant is already faced with absorbing the hardware businesses of Sun Microsystems, which Oracle purchased earlier in 2010.

According to a report in TheStreet, there are also rumors that Microsoft might buy EMC, but these were called "implausible." Avian Securities analyst Matt Bryson, who was quoted in TheStreet report, suggested that a deal in which Microsoft buys EMC's VMware could be a more likely possibility.

If Microsoft were interested in a VMware deal, the company would be unlikely to say so publicly. VMware makes the most widely used x86 virtualization platform, but Microsoft seems to believe its strategy of integrating an affordable hypervisor into Windows Server will win out over VMware's more expensive virtualization software in the end.